I'm having a little trouble following your results and your conclusion. As you say, it's hard to show this kind of data. I would order the states by percentage of African American population, and then highlight key examples of where it does or does not correlate to a high instance of searing for "ebony" porn.
If I read your post right, you're saying that people are specifically looking for pornography featuring people who look like them, so more black people = more black porn. You certainly see this if you start looking at the international results: Japan, for example, has the word "Japan" or Japanese" in almost every result. The same held true in several other countries to lesser extents. Here, however, you seem to be suggesting that the Data doesn't really support they hypothesis. Is that right?
If that's the case, I can see two alternate hypotheses that could be considered:
One is that people are more likely to see people of other races as undesirable in a more recently segregated part of the country, and so black people in the south are more likely to want to see black people in their porn then black people in the north do. I'm not sure this holds up because there is no tendency for southern states to specify ethnicity otherwise, though presumably white searchers might find it unnecessary because the majority of most searches will come up white.
The second possibility is that white people in the south who desire sex with black people often do not get to pursue them publicly. In this vein, it is notable that so called "bible belt" states are more likely then non-bible-belt states to have "gay" in the top 10.
The third possibility is that the very taboo-ness of it makes it more exciting for some searchers. There's nothing terribly taboo about mixing races in some parts of the country, but there is still a taboo about it in the south. I have a friend who went to school in rural Kentucky, and to hear him tell it, every time he had sex with a white girl, she would make some comment about how much it would piss off her father.